Transport, Sensitivity and Uncertainty Analysis of FNG 14 MeV Neutron Bulk Shield Experiment

Abstract

Bulk Shield experiment representing a mock-up of the ITER inboard blanket and vacuum vessel was completed in 1997 at the 14 MeV Frascati Neutron Generator (FNG) at ENEA Frascati. The objective of the experiment was to verify the calculational methods and nuclear data files used in the design and shielding calculations for fusion reactor. The benchmark experiment was analysed using the discrete ordinates transport code DORT, and the sensitivity and uncertainty analysis code package SUSD3D developed within the EFF project. Neutron cross-sections taken from FENDL-1 and FENDL-2 evaluations were used in the transport calculation. The results were compared with the measured reaction rates and with those calculated by the Monte Carlo code MCNP4A using FENDL-1. Good agreement between MCNP and DORT results was observed. No significant difference between FENDL-1 and FENDL-2 results was found, FENDL-2 performing slightly better. The transport calculations were combined with the sensitivity and uncertainty analysis whose application has proven to be very useful in order to obtain information on the importance of various nuclear data in the neutron transport, to explain the discrepancies between the calculation and the measurement, or at least to discard some possible reasons for the discrepancy. The sensitivity analysis coupled with the covariance matrices can guide future nuclear data research and development.